feat: track TCP connection state (#217)

Depends on #206

This PR makes the TCP module store a state for each TCP connection and
compute the sequence and ACK numbers for each segment, according to [RFC
9293](https://datatracker.ietf.org/doc/html/rfc9293#name-other-states).

Author: MegaRedHand

src/packets/tcp.ts

@@ -9,6 +9,9 @@ import { Ports } from "./ip";
 
 export const TCP_FLAGS_KEY = "tcp_flags";
 
+// 2 bytes number
+export type Port = number;
+
 export class Flags {
   // Urgent Pointer field significant
   public urg = false;
@@ -92,10 +95,10 @@ export class TcpSegment implements IpPayload {
   //
   // 2 bytes
   // The source port number.
-  sourcePort: number;
+  sourcePort: Port;
   // 2 bytes
   // The destination port number.
-  destinationPort: number;
+  destinationPort: Port;
   // 4 bytes
   // The sequence number of the first data octet in this segment (except
   // when SYN is present). If SYN is present the sequence number is the
@@ -147,10 +150,10 @@ export class TcpSegment implements IpPayload {
   constructor(
     srcPort: number,
     dstPort: number,
-    seqNum: number,
-    ackNum: number,
-    flags: Flags,
-    data: Uint8Array,
+    seqNum = 0,
+    ackNum = 0,
+    flags: Flags = new Flags(),
+    data: Uint8Array = new Uint8Array(0),
   ) {
     checkUint(srcPort, 16);
     checkUint(dstPort, 16);
@@ -165,6 +168,16 @@ export class TcpSegment implements IpPayload {
     this.data = data;
   }
 
+  withFlags(flags: Flags): TcpSegment {
+    this.flags = flags;
+    return this;
+  }
+
+  withData(data: Uint8Array): TcpSegment {
+    this.data = data;
+    return this;
+  }
+
   computeChecksum(): number {
     const segmentBytes = this.toBytes({ withChecksum: false });
 

src/programs/http_client.ts

@@ -3,6 +3,7 @@ import { ProgramInfo } from "../graphics/renderables/device_info";
 import { DeviceId } from "../types/graphs/datagraph";
 import { ViewGraph } from "../types/graphs/viewgraph";
 import { Layer } from "../types/layer";
+import { AsyncQueue } from "../types/network-modules/asyncQueue";
 import { TcpSocket } from "../types/network-modules/tcpModule";
 import { ViewHost } from "../types/view-devices";
 import { ProgramBase } from "./program_base";
@@ -66,7 +67,7 @@ export class HttpClient extends ProgramBase {
 
     // Read response
     const buffer = new Uint8Array(1024);
-    const readLength = await socket.read(buffer);
+    const readLength = await socket.readAll(buffer);
     if (readLength < 0) {
       console.error("HttpClient failed to read from socket");
       return;
@@ -85,6 +86,8 @@ export class HttpServer extends ProgramBase {
 
   private port: number;
 
+  private stopChannel = new AsyncQueue<"stop">();
+
   protected _parseInputs(inputs: string[]): void {
     if (inputs.length !== 0) {
       console.error(
@@ -105,8 +108,7 @@ export class HttpServer extends ProgramBase {
   }
 
   protected _stop() {
-    // Nothing to do
-    // TODO: stop serving requests
+    this.stopChannel.push("stop");
   }
 
   private async serveHttpRequests() {
@@ -124,11 +126,17 @@ export class HttpServer extends ProgramBase {
       return;
     }
 
+    const stopPromise = this.stopChannel.pop();
+
     while (true) {
-      const socket = await listener.next();
+      const socket = await Promise.race([stopPromise, listener.next()]);
+      if (socket === "stop") {
+        break;
+      }
 
       this.serveClient(socket);
     }
+    listener.close();
   }
 
   // eslint-disable-next-line @typescript-eslint/no-unused-vars
@@ -139,7 +147,7 @@ export class HttpServer extends ProgramBase {
 
   async serveClient(socket: TcpSocket) {
     const buffer = new Uint8Array(1024).fill(0);
-    const readLength = await socket.read(buffer);
+    const readLength = await socket.readAll(buffer);
 
     // eslint-disable-next-line @typescript-eslint/no-unused-vars
     const readContents = buffer.slice(0, readLength);